These commands search the registered nicknames/channels for ones
matching the provided regex, or return the entire list.

Only operators with chanreg (for ChanServ) or accreg (for NickServ)
capabilities can use LIST.

Or try to, anyway

In the previous commit, the client would receive a failure message but would
actually remain logged in after an authzid/authcid mismatch. This was a
correctness rather than a security issue, but now it's fixed so that the client
never logs in in the first place.

* Fix #684
* Fix #683
* Add `CHANSERV CLEAR`
* Allow mode changes from channel founders even when they aren't joined
* Operators with the chanreg capability are exempt from max-channels-per-account
* Small fixes and cleanup

1. DRY "banner" descriptions of each services
2. `/HELP NICKSERV` now refers the user to `/NICKSERV HELP`, etc.
3. Fix double translation of `textGenerator` output

Standard nickserv clients like znc's expect (by default) to send just:

PRIVMSG NickServ :identify $passphrase

with the account name assumed to be the currently held nick.

Let's support this in the common case where the client doesn't have a certfp
(if it does, the first argument is the account name, not the passphrase).